Martínez-Millán, M., W. L. Crepet, and K. C. Nixon. 2009. Pentapetalum trifasciculandricus gen. et. sp. nov., a thealean fossil flower from the Raritan formation, New Jersey, USA (Turonian, Late Cretaceous). American Journal of Botany 96 (5): 933-949.

Abstract: The study of fossil flowers in the last 25 years has greatly increased our understanding of angiosperm diversification. Following that tradition, we here describe a new fossil taxon from the Late Cretaceous of New Jersey, Pentapetalum trifasciculandricus Martínez-Millán, Crepet et Nixon gen. et sp. nov. It includes actinomorphic pentamerous fl owers with quincuncial calyx, imbricate corolla, numerous stamens of markedly different heights, and a superior tricarpellate ovary, which are morphologically consistent with the flowers of the Theaceae s.l . and of members of the order Theales sensu Cronquist. Cladistic analyses including 45 extant taxa plus the fossil, 61 morphological characters, and different combinations of the molecular markers rbcL, matK, trnL-trnF, matR, and ITS support its inclusion in the order Ericales sensu APG. Comparison with extant taxa using traditional methods of identification suggests a relation with the Theaceae s.s. (Stewartia), but the phylogenetic analyses do not support this view. Instead, the phylogenetic analysis suggests some relation to the Ternstroemiaceae/Pentaphylacaceae (Theaceae s.l.), exemplifying the importance of evaluating identifications in a phylogenetic context. The description of Pentapetalum further adds to the ample diversity of Ericales in the Late Cretaceous.

FOSSIL PHOTOS

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Pentapetalum trifasciculandricus
Actual width in ( ) unless otherwise noted.

Top view of flower
(Maximum diameter= 1.29 mm)
Side view of flower
(height= 1.50 mm)
Dissected flower showing
internal structures
(height= 1.29 mm)

Ovules
(height= 200 µm)
Group of Stamens
(width at base= 546 µm)
Pollen grain
(length= 11 µm)